Wireless communication systems are ubiquitous for personal and commercial uses. Demand for such systems continues to increase as the quantity of users, devices, and data increases. However there is a limit to the number of signals a communication system can accommodate per the number of orthogonal or quasi-orthogonal codes, for a direct sequence spread spectrum application. This is because the communication system is an interference limited and/or a code limited resource.
Data signals, or simply signals, are sequences of finite length repeating periodically. A signal of length n, can be represented as a vector in an n-dimensional space of complex number or equivalently as a complex-valued function.
In direct-sequence spread spectrum (DSSS) communication systems, multiple signals with different encoding sequences are transmitted simultaneously. To retrieve the desired data stream from the overall data signal, the specific code sequence used to encode the desired signal is reproduced at a receiver, and via the autocorrelation properties, used to detect the original data stream from the noise of and interference in the overall signal.
In a code division multiple access (CDMA) communication systems, a multiple access technique in which a plurality of substantially orthogonal codes are used to spread spectrum modulate user signals within a system. Each modulated user signal may have an overlapping frequency spectrum with other modulated user signals in the system. However, because the underlying modulation codes are orthogonal, it is possible to demodulate individual user signals by performing a correlation operation using the appropriate code. As can be appreciated, a communication device operating within a CDMA-based system will often receive overlapping communication signals associated with a variety of different users. The signals associated with other users will typically appear as interference when trying to demodulate a signal associated with a desired user within the communication device.
The above-described background is merely intended to provide an overview of information regarding wireless communication networks, and is not intended to be exhaustive. Additional context may become apparent upon review of one or more of the various non-limiting embodiments of the following detailed description.